As mentioned, some of the programs listed in the resources can work well. Many of the ones that depict creating dungeons from tiles will work just as well making cities similarly, all you need to do is look for the tiles on Google.

If you're just looking for a map to show players, not to have their tokens actually use to move, I recommend drawing a basic one by hand or, if you're so inclined, on something like GIMP on the computer. I draw maps like these by hand, and while yes it will take an hour or two of slowly drawing to get them to look decent unless you are already good at drawing, I find they look better at the end, and are far more unique.

If you are looking for token-sized battle map towns, and none of the programs fit your fancy on the sidebar, download some tile packs around the net/Google and use GIMP or hell even MSPaint and piece them together. I recommend GIMP over Paint since you can make a grid sized for the tiles for ease of creation.

If you play using Roll20, you can get tile packs through them and build your towns in their editor easily. Done this for a campaign as well, works like a charm.